Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())
S = [input() for _ in range(H)]

c = [[-1 for _ in range(W)] for _ in range(H)]
d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
q = deque()
q.append((0, 0))
c[0][0] = 1

while q:
    x, y = q.popleft()
    for dx, dy in d:
        nx = x + dx
        ny = y + dy
        if nx < 0 or nx >= W or ny < 0 or ny >= H:
            continue
        if S[ny][nx] == "." and c[ny][nx] is -1:
            c[ny][nx] = c[y][x] + 1
            q.append((nx, ny))

c_min = c[H - 1][W - 1]

if c_min == -1:
    ans = -1
else:
    ans = sum([s.count(".") for s in S]) - c_min

print(ans)